Module documentation for 0.0.3.1

The documentation of "System.Environment.getProgName" says that
"However, this is hard-to-impossible to implement on some non-Unix OSes,
so instead, for maximum portability, we just return the leafname
of the program as invoked."
This library tries to provide the missing path.
Note: Since base 4.6.0.0, there is also a function
"System.Environment.getExecutablePath".